I would suggest 5 x 70GB on each SSD for the RocksDB and WAL in the same
partition/LVM.
Unless you have a plan in the future to add some faster NVME for the WAL's when
you might want them in a separate partition to make it easier to move the WAL
to the NVME.
Darren
On 04/09/2019, 10:12, "Yoann Moulin" <yoann.mou...@epfl.ch> wrote:
Le 04/09/2019 à 11:01, Lars Täuber a écrit :
> Wed, 4 Sep 2019 10:32:56 +0200
> Yoann Moulin <yoann.mou...@epfl.ch> ==> ceph-users@ceph.io :
>> Hello,
>>
>>> Tue, 3 Sep 2019 11:28:20 +0200
>>> Yoann Moulin <yoann.mou...@epfl.ch> ==> ceph-users@ceph.io :
>>>> Is it better to put all WAL on one SSD and all DBs on the other one?
Or put WAL and DB of the first 5 OSDs on the first SSD and the 5 others on
>>>> the second one.
>>>
>>> I don't know if this has a relevant impact on the latency/speed of the
ceph system but we use LVM on top of a SW RAID 1 over two SSDs for WAL & DB on
this RAID1.
>>
>> What is the recommended size for wall and db in my case?
>>
>> I have :
>>
>> 10x 6TB Disk OSDs (data)
>> 2x 480G SSD
>>
>> Best,
>
> I'm still unsure with the size of the block.db and the wal.
> This seems to be relevant:
> http://lists.ceph.com/pipermail/ceph-users-ceph.com/2019-May/035086.html
>
> But it is also said that the pure WAL need just 1 GB of space.
>
http://lists.ceph.com/pipermail/ceph-users-ceph.com/2019-August/036509.html
>
> So the conclusion would be to use 2*X(DB) + 1GB (WAL) if you put both on
the same partition/LV.
> With X being on of 3GB, 30GB or 300GB.
>
> You have 10 OSDs. That means you should have 10 partitions/LVs for DBs &
WALs.
So, I don't have enough space on SSDs to do raid1, I must use 1 SSD for 5
disks.
5x64GB + 5x2GB should be good, shouldn't it?
And I still don't know if the ceph-ansible playbook can manage the LVM
setup of shall I need to prepare all VG and LV before.
Best,
--
Yoann Moulin
EPFL IC-IT
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